Intermetallic compounds, producing blue and purple golds, as well as other colors. These are typically brittle but can be used as gems and inlays

Surface treatments such as oxide layers

Pure 100% gold is 24 karat by definition, so all colored golds are less than this, with the common being 18K (75%), 14K (58%), and 9K (38%).

Rose gold is a gold and copper alloy widely used for specialized jewelry. Rose gold, also known as pink gold and red gold, was popular in Russia at the beginning of the nineteenth century, and was also known as Russian gold although this term is now obsolete. Rose gold jewelry is becoming more popular in the 21st century and is commonly used for wedding rings, bracelets, and other jewelry.

Although the names are often used interchangeably, the difference between red, rose, and pink gold is the copper content: the higher the copper content, the stronger the red coloration. Pink gold uses the least copper, followed by rose gold, with red gold having the highest copper content. Examples of the common alloys for 18K rose gold, 18K red gold, and 18K pink gold:

18K Red gold: 75% gold, 25% copper

18K Rose gold: 75% gold, 22.25% copper, 2.75% silver

18K Pink gold: 75% gold, 20% copper, 5% silver

12K Red gold: 50% gold and 50% copper.

Up to 15% zinc can be added to copper-rich alloys to change their color to reddish yellow or dark yellow.

During ancient times, due to impurities in the smelting process, gold frequently turned a reddish color. This is why many Greco-Roman texts, and even many texts from the Middle Ages, describe gold as "red".

Eighteen karat red gold may be made of 25% copper and 75% gold. For 18 karat rose gold, typically about 4% silver is added to 75% gold and 21% copper to give a rose color. 14 karat red gold is often found in the Middle East and contains 41.67% copper.

High-end flutes are very commonly made of solid rose gold, the most common alloy being 14K.

22 Gauge 18K Solid Rose Gold Wire was used in the electrolysis process: